Colorado police department mistakenly destroyed DNA evidence in dozens of sexual assault cases. Leading the attackers likely to escape justice. Police in a -- near Denver. Reveal evidence in 48 assaults in 2009 was inadvertently destroyed by an officer. Temporarily assigned to the department's evidence unit it is already derailed one prosecution. And the police chief says it's -- -- these suspects in the rest of the cases were prosecuted without that evidence the department. Is now investigating exactly how such serious mistakes -- made. Chief says he's already personally apologize to one victim who's accused attacker got to walk free.

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